Hygroscopic apparatus



May '5, 1936;

c. L. BURDICK HYGROSCOPIC APPARATUS Filed Nov. 15, 1933 Patented May 5, 1936 UNITED STATES PATENT OFFICE Application November 15, 1933, Serial No. 698,159 In Germany April 1, 1933 1 Claim.

This invention relates to hygroscopic apparatus or instruments of the class which are motivated by changes in the moisture content of the surrounding air or other gases.

The present invention is more particularly an improvement over the apparatus disclosed in my prior United States Letters Patent No. 1,932,012 of October 24, 1933.

The primary object of the invention is to provide means whereby the change in dimension of the fibre from the outer covering of the ovular bracts of conifer trees responsive to a change in humidity of the surrounding gas may be translated into mechanical movements to actuate an indicator or register.

A further object of the invention is to provide means whereby the movement of the fibres is confined to a linear expansion or contraction.

Another object of the invention is to provide means whereby the hygrostatic element comprising the fibres from ovular bracts of conifer trees may be used in automatic control of humidity, either direct or by means of a power relay.

Further objects and advantages of the invention will become apparent as the description proceeds with reference to the accompanying drawing in which:

Figure 1 is a plan view of one form of a registering hygrometer, Figure 2 is a side elevation, and Figure 3 a side view of a detail of same.

Referring to the drawing, a pointer l is mounted on a stud or axle 2 and arranged to travel over a calibrated scale 3. Two strips of fibre 4 and 4' are made up from the outer covering of the ovular bracts of conifer trees. The longer fibres in this outer covering are very sensitive to moisture, and when separated from the other portions of the bract and reduced to thin, narrow strips respond quickly to changes of humidity in the air, that is, they are lengthened with an increase of the percentage of moisture and shortened upon desiccation. The strips 4 and 4' are made up of short lengths of the fibre which may be joined by binding, stitching, or any other suitable means. One end of the piece 4 is secured to an adjustable terminal 5 into which an adjusting screw 6 is threaded, the latter being carried by a stationary bracket 6. The initial tension given the strip 4 is regulated by this adjustment. The other end of the strip 4 is secured to one end of a pivoted adjustable lever having two arms 1 and I, which are mounted on a stud 8. To the arm 1' of this lever the jointed fibre strip 4 is secured and. the other end of this strip is fastened to an adjustable lever having arms l2 and I2 mounted on a stud l3. A cord or chain is secured to the arm l2 and wrapped around the shaft 2 which carries the pointer I. A spring l4 moves the pointer in one direction and it will be seen that desiccation of the strips of fibre 4 and 4 will move the pointer in the opposite direction.

Mechanism for adjusting the effective length of the compound lever 1l' is provided and consists of adjusting discs 9 and 9'. Openings are provided in the adjusting discs 9 and 9, one of the openings in each disc being eccentric, as shown in Fig. 1, and the other opening being of sufficient size to leave the eccentric slots, or openings, unobstructed. Tongues l0 and I0 are pressed out from the levers I and l and bent so as to fall, after passing through the openings in the discs 9 and 9', into suitable slots, or openings, in the opposite ends of the respective levers. It will thus be seen that the tongues l0 and 10' are engaged with the plates 9 and 9' through the eccentric slots in the latter so that upon rotation of the plates the effective length of the lever arms I and I may be lengthened or shortened. By moving the discs in relation to each other the amplitude of movement of the pointer is controlled.

By altering the relative angular positions of the arms I! and I2 about the stud l3 a variation in the leverage at either end of movement of the pointer is had. A screw l4 threaded into the arm l2 bears upon the inner-end of the arm I! and holds the two rigidly together in any selected position.

' While the invention has been illustrated and described in connection with humidity controls, it is obvious that it may be adapted to operate other forms of automatic or semi-automatic apparatus or instruments, as for controlling electric current or other motive power either direct or by means of relays, in response to changes in the humidity of the atmosphere. The above described form of construction is given by way of example and I do not restrict my invention to the precise structure disclosed.

What I claim is:

An element linearly responsive to changes in the humidity of a surrounding gaseous medium, said element comprising a strip made up of a plurality of united fibrous segments from the ovular bracts of conifer trees.

CHARLES L. BURDICK. 

